Effect of Freeze-Thaw Action on Porosity Change and Destruction of Weathered Bedrock in Different Lithology and Development of Destruction Model

Abstract

A freeze-thaw experiment was conducted to investigate the destruction mode of weathered bedrock in different lithologies. The experiment was conducted on bedrock samples of weathered granite (WGr), weathered granite porphyry (WGp), weathered shale (WS), weathered sandstone (WSa) and weathered rhyolite (WR). Because of freeze and thaw action, porosity of the bedrock samples increased and weight of the samples decreased. When porosity of WGr, WGp and WS increased greater than 0.43, 0.1 and 0.27, respectively, small pieces were detached from the main sample bodies. In contrast, freezing and thawing caused only slight increases in the porosity of WSa and WR and production of fine sediment from the surface. Depth of the sediment productions of WSa and WR due to one freeze-thaw cycle was equivalent to less than 1.0 and 0.2 mm, respectively. Hence, these rocks are exposed to only slight damage, which are at the ground surface. The experimental results were also used for developing a simple destruction model.

A combined model of sediment production, supply and transport

“…Subsequently, wind, gravity, surface flows, and raindrops can remove the soil and displace it to the toe of the slope; thus, talus is formed at the sides of the channel. Considering the mechanisms of such a sediment production process, Izumiyama et al (2012) presented a method for estimating the annual sediment production rate for different geologies. They classified the production rates into two groups for different types of bedrock, namely, those for soft bedrock (e.g.…”

“…Here, the method of Izumiyama et al (2012) was employed for simulating sediment production from the weathering of bedrock located on bare slopes. The annual sediment production rate, which was expressed by the annual erosion depth, is described as follows:…”

“…Sediment production is defined as the generation of fresh soil through the weathering of bedrock, landslides, gully erosion, volcanic eruptions, and so forth. Izumiyama et al (2012) argued that freeze-thaw action is an important process in the final stages of sediment production, and proposed a numerical simulation model that can estimate the amount of sediment production based on topographical, meteorological and geological data. Following sediment production in mountainous regions, the generated sediment forms talus deposits at the toe of slopes.…”

“…In this study, we investigate the actual sediment runoff process in an experimental basin at the Hodaka Sedimentation Observatory, Kyoto University, Japan, and develop an integrated model to describe sediment runoff. The numerical simulation method for the sediment production process due to freeze-thaw action proposed by Izumiyama et al (2012) was employed here. A talus erosion model was developed to simulate sediment supply.…”